Work is currently under way in three areas involving statistical modelling of biological information systems. The first area deals with the so-called Stein model of neural integration and firing which is in essence a continuous time continuum state Markov process. This process is mathematically described by a first order delay and advance type partial differential equation and numerical methods of solution have been developed for this system. The second area involves an investigation of the statistical interdependence of adjacent bases in mitochondrial, prokaryotic and eukaryotic DNA. It is found that the third base position of the codon has different dependencies for the three mentioned classes of DN. The third area of probabilistic modelling is aimed at developing a mathematical description of pitch perception based on known models of cohlear mechanics and postulated mechanisms of neural processing in an attempt to give a theory consistent with such phenomena as masking, critical bands, and missing fundamentals. Work is just beginning in this area.